In these applications, the operators who do not always have a very clear view as to the future distribution of the traffic (and therefore of the power) over the coverages addressed need to have a certain flexibility making it possible to adapt the satellite throughout its lifetime to the traffic needs resulting from the demand and the success of the service over different geographic zones. It is therefore important to be able to route the channels in a flexible way to the beams, that is to say, in such a way that the total number of channels handled by the payload can be distributed to the different beams in accordance with the traffic demand, throughout the lifetime of the satellite.
In order to ensure this flexibility, it is known practice to use a distributed amplification in which all the amplifiers placed in parallel amplify all the input channels of the payload.
According to this architecture, the channels are combined before amplification, the amplification is common to all the channels and each amplifier feeds all beams signals. This architecture is compatible with the amplification of any frequency distribution of the channels.
The article by P. Angeletti et al., entitled “Multiport Power Amplifiers for Flexible Satellite Antennas and Payloads,” published in the Microwave Journal of May 2010, describes the general principle whereby the architecture of a telecommunications payload, reconfigurable in real time to distribute the radiofrequency (RF) power available as a function of the demand, is based on the possibility of making use of a reservoir or bank of radioelectric power, formed by a set of amplifiers arranged in parallel, and which implements a distributed amplification of one or more signals, each of the signals being amplified by all the amplifiers.
The article by P. Angeletti describes examples of architectures illustrating this general principle like the multibeam mobile communications repeater of the Japanese satellite ETS-VI, the mobile communications repeaters of the MTSAT-1 and MTSAT-2 satellites, and the mobile communications payload of the Inmarsat-3 satellite.
The article by I. Hosoda et al., entitled “Ka band high power multiport amplifier (MPA) configured with TWTA for WINDS satellite,” IEEE 2007, describes the architecture of a reconfigurable telecommunication payload using the principle of distributed amplification.
While the principle of distributed amplification as described above addresses the problem of real-time adaptation of the payload available RF power to traffic requirements, problems arise of the paralleling of amplifiers over a total transmission band wider than those currently used and the implementation of a redundancy scheme (back-up amplifiers) compatible with this wideband constraint.
In effect, the conventional current systems operate over relatively narrow bands. For example, the multiport amplifier MPA of the WINDS satellite operates in the Ka band with 6% of the useful band. In these conventional systems, amplifiers individual adjustment is typically performed at the central frequency of the band to be handled, which limits the correction over the entire band. When seeking to increase the transmission bandwidth, gain and phase dispersion increases at the edges of the band, and it exceeds the dispersion that is “acceptable” to have a good power recombination.
Now, operation of a distributed amplification device over wider useful transmission bands is desirable, for example a useful band of 2 GHz at the frequency of 11.7 GHz for the Ku band.
The patent application WO 2008/017699 A1 describes a solution to the above problem by proposing an architecture in which a distributed amplification device amplifies and distributes in a flexible way a plurality of s input transmission channels to an output corresponding to an antenna beam with acceptable performance in terms of amplifiers amplitude and phase dispersion adjustment over a wide frequency band.
The proposed distributed amplification device comprises frequency band combination means comprising s inputs for receiving the s transmission channels and q outputs for respectively supplying the transmission channels grouped together within q frequency bands, power amplification means including p active amplifiers, arranged in parallel for the channels distributed amplification, and gain and phase setting means associated with the p power amplifiers over the q frequency bands.
However, even though this architecture allows a gain and phase alignment between amplifiers over a wide frequency bandwidth and thus the use of paralleled amplifiers in flexible payloads multichannel applications, distribution of the transmission channels according to the q frequency bands and the use of p active amplifiers induce the need to use q*p phase-shifters/attenuators, which results in a more complex solution because of the use of controllable phase-shifters and attenuators.
Furthermore, the proposed architecture describes settings made upstream of the eight amplifiers set considered in principle to be nominal amplifiers and therefore the settings of a single nominal routing configuration. The document WO 2008/017699 A1 does not describe the consideration of gain and phase setting means for effects induced by routing reconfigurations which implement back-up configurations involving one or more back-up amplifiers.
The effects induced by a switch to the back-up amplifiers are caused notably by the introduction of electrical length disparities between the active amplification paths created upon the reconfiguration by input and output redundancy rings, and these effects increase the gain and phase dispersion of the active amplification pathways, all the more so as the useful transmission total bandwidth increases.
Thus, for all the architectures of redundant distributed amplification devices known to date, when seeking to extend the useful transmission band to achieve a wideband of use of the reservoir within the observance of an acceptable gain and phase dispersion of the active amplification pathways of one and the same configuration, an amplitude and phase equalization of said amplification pathways or paths of the reservoir by conventional gain and phase setting means over all of the nominal and back-up operating configurations of the reservoir does not allow for such wideband extension.
A first technical problem is to propose an architecture of a redundant distributed amplification device which reduces, over a wideband, the gain and phase dispersion of the active amplification pathways of one and the same configuration.
A second technical problem, connected to the first problem, is to propose a redundant distributed amplification device which makes it possible, with sufficient performance in terms of acceptable dispersion, to equalize, in amplitude and in phase over a wideband, the internal active amplification paths of all the operating configurations of the device.